Soft magnetic metallic glass alloy

ABSTRACT

Disclosed is a soft magnetic Fe—B—Si-based metallic glass alloy with high glass forming ability which has a supercooled-liquid temperature interval (ΔT χ ) of 40 K or more, a reduced glass-transition temperature (T g /T m ) of 0.56 or more and a saturation magnetization of 1.4 T or more. The metallic glass alloy is represented by the following composition formula: (Fe 1-a-b B a Si b ) 100-χ M χ , wherein a and b represent an atomic ratio, and satisfy the following relations: 0.1≦a≦0.17, 0.06≦b≦0.15 and 0.18≦a+b≦0.3, M is one or more elements selected from the group consisting of Zr, Nb, Ta, Hf, Mo, Ti, V, Cr, Pd and W, and χ satisfies the following relation: 1 atomic % ≦χ≦10 atomic %. The present invention overcomes restrictions in preparing a metallic glass bar with a thickness of 1 mm or more from conventional Fe—B—Si-based metallic glasses due to their poor glass forming ability, and provides a high saturation-magnetization Fe—B—Si-based metallic glass allowing the formation of bulk metallic glass, which serves as a key technology for achieving a broader application fields of metallic glass products.

TECHNICAL FIELD

The present invention relates to a soft magnetic Fe—B—Si-based metallicglass alloy with high saturation magnetization and high glass formingability.

BACKGROUND ART

Conventional metallic glasses include Fe—P—C-based metallic glass whichwas first produced in the 1960s, (Fe, Co, Ni)—P—B-based alloy, (Fe, Co,Ni)—Si—B-based alloy, (Fe, Co, Ni)—(Zr, Hf. Nb)-based alloy and (Fe, Co,Ni)—(Zr, Hf, Nb)—B-based alloy which were produced in the 1970s.

All of the above alloys are essentially subjected to a rapidsolidification process at a cooling rate of 10⁴ K/s or more, and anobtained sample is a thin strip having a thickness of 200 μm or less.Between 1988 and 2001, various metallic glass alloys exhibiting highglass forming ability, which have a composition, such as Ln—Al-TM,Mg—Ln-TM, Zr—Al-TM, Pd—Cu—Ni—P, (Fe, Co, Ni)—(Zr, Hf. Nb)—B, Fe—(Al,Ga)—P—B—C, Fe—(Nb, Cr, Mo)—(Al, Ga)—P—B—C, Fe—(Cr, Mo)—Ga—P—B—C,Fe—Co—Ga—P—B—C, Fe—Ga—P—B—C or Fe—Ga—P—B—C—Si (wherein Ln is arare-earth element, and TM is a transition metal), were discovered.These alloys can be formed as a metallic glass bar having a thickness of1 mm or more.

The inventor previously filed patent applications concerning a softmagnetic metallic glass alloy of Fe—P—Si—(C, B, Ge)-(group-IIIB metalelement, group-IVB metal element) (Patent Publication 1); a softmagnetic metallic glass alloy of (Fe, Co, Ni)—(Zr, Nb, Ta, Hf, Mo, Ti,V)—B (Patent Publication 2); and a soft magnetic metallic glass alloy ofFe—(Cr, Mo)—Ga—P—C—B (Patent Publication 3).

Parent Publication 1: Japanese Patent Laid-Open Publication No. 11-71647

Parent Publication 2: Japanese Patent Laid-Open Publication No.11-131199

Parent Publication 3: Japanese Patent Laid-Open Publication No.2001-316782

DISCLOSURE OF INVENTION

The inventor previously found out several soft magnetic bulk metallicglass alloys with a saturation magnetization of up to 1.4 T. However, inview of practical applications, it is desired to provide a soft magneticmetallic glass alloy having a saturation magnetization of 1.4 T or more.

Through researches on various alloy compositions in order to achieve theabove object, the inventor found a soft magnetic Fe—B—Si-based metallicglass alloy composition exhibiting clear glass transition and widesupercooled liquid region and having higher glass formation ability andhigher saturation magnetization, and has accomplished the presentinvention.

Specifically, the present invention provides a soft magneticFe—B—Si-based metallic glass alloy with high glass forming ability whichhas a supercooled-liquid temperature interval (ΔT_(χ)) of 40 K or more,a reduced glass-transition temperature (T_(g)/T_(m)) of 0.56 or more anda saturation magnetization of 1.4 T or more. The metallic glass alloy isrepresented by the following composition formula:(Fe_(1-a-b)B_(a)Si_(b))_(100-χ)M_(χ), wherein a and b represent anatomic ratio, and satisfy the following relations: 0.1≦a≦0.17,0.06≦b≦0.15 and 0.18≦a+b≦0.3, M is one or more elements selected fromthe group consisting of Zr, Nb, Ta, Hf, Mo, Ti, V, Cr, Pd and W, and χsatisfies the following relation: 1 atomic %≦χ≦10 atomic %.

In a metallic glass prepared using the alloy with the above compositionthrough a single-roll rapid liquid cooling process in the form of thinstrip (or film, ribbon) having a thickness of 0.2 mm or more, asupercooled-liquid temperature interval (or the temperature interval ofa supercooled liquid region) (ΔT_(χ)), which is expressed by thefollowing formula: ΔT_(χ)=T_(χ)−T_(g) (wherein T_(χ) is acrystallization temperature, and T_(g) is a glass transition(vitrification) temperature), is 40 K or more, and a reducedglass-transition temperature (T_(g)/T_(m)) is 0.56 or more.

During the course of preparing a metallic glass using the liquid alloywith the above composition through a cupper-mold casting process, heatgeneration caused by significant glass transition and crystallization isobserved in a thermal analysis. A critical thickness or diameter inglass formation is 1.5 mm. This proves that metallic glass can beprepared through a cupper-mold casting process.

In the above alloy composition of the present invention, a primarycomponent or Fe is an element playing a role in creating magnetism.Thus, Fe is essentially contained in an amount of 64 atomic % or more toobtain high saturation magnetization and excellent soft magneticcharacteristics, and may be contained in an amount of up to 81 atomic %.

In the above alloy composition of the present invention, metalloidelements B and Si play a role in forming an amorphous phase. This roleis critical to obtain a stable amorphous structure. InFe_(1-a-b)B_(a)Si_(b), the atomic ratio of a+b is set in the range of0.18 to and 0.3, and the remainder is Fe. If the atomic ratio of a+b isoutside this range, it is difficult to form an amorphous phase. It isrequired to contain both B and Si. If either one of B and Si is outsidethe above composition range, the glass forming ability is deterioratedto cause difficulties in forming a bulk metallic glass.

In the above alloy composition of the present invention, the addition ofthe element M is effective to provide enhanced glass forming ability. Inthe alloy composition of the present invention, the element M is addedin the range of 1 atomic % to 10 atomic %. If the element M is outsidethis range and less than 1 atomic %, the supercooled-liquid temperatureinterval (ΔT_(χ)) will disappear. If the element M is greater than 10atomic %, the saturation magnetization will be undesirably reduced.

The Fe—B—Si-based alloy of the present invention may further contain 3atomic % or less of one or more elements selected from the groupconsisting of P, C, Ga and Ge. The addition of the one or more elementsallows a coercive force to be reduced from 3.5 A/m to 3.0 A/m, orprovides enhanced soft magnetic characteristics. On the other hand, ifthe content of the one or more elements becomes greater than 3 atomic %,the saturation magnetization will be lowered as the content of Fe isreduced. Thus, the content of the one or more elements is set at 3atomic % or less.

In the above alloy composition of the present invention, any deviationfrom the above defined composition ranges causes deteriorated glassforming ability to create/grow crystals during the process ofsolidification of liquid metals so as to form a mixed structure of aglass phase and a crystal phase. If the deviation from the compositionrange becomes larger, an obtained structure will have only a crystalphase without any glass phase.

The Fe—B—Si alloy of the present invention has high glass formingability allowing a metallic glass round bar with a diameter of 1.5 mm tobe prepared through a copper-mold casting process. Further, at the samecooling rate, a thin wire with a minimum diameter of 0.4 mm can beprepared through an in-rotating-water spinning process, and a metallicglass powder with a minimum particle diameter of 0.5 mm through anatomization process.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is an optical micrograph showing the sectional structure of acast bar in one Inventive Example.

FIG. 2 is a graph showing thermal analysis curves of a cast bar obtainedin Inventive Example 1 and a ribbon obtained in Inventive Example 15.

FIG. 3 is a graph showing thermal analysis curves of a cast bar obtainedin Inventive Example 3 and a ribbon obtained in Inventive Example 16.

FIG. 4 is a graph showing I-H hysteresis curves of the cast bar obtainedin Inventive Example 1 and the ribbon obtained in Inventive Example 15,based on the measurement of their magnetic characteristics using avibrating-sample magnetometer.

FIG. 5 is a graph showing I-H hysteresis curves of the cast bar obtainedin Inventive Example 3 and the ribbon obtained in Inventive Example 16,based on the measurement of their magnetic characteristics using avibrating-sample magnetometer.

FIG. 6 is a schematic side view of an apparatus for use in preparing analloy sample of a cast bar through a copper-mold casting process.

BEST MODE FOR CARRYING OUT THE INVENTION INVENTIVE EXAMPLES 1 TO 14,COMPARATIVE EXAMPLES 1 TO 7

FIG. 6 is a schematic side view of an apparatus used in preparing analloy sample with a diameter of 0.5 to 2 mm through a copper-moldcasting process. A molten alloy 1 having a given composition was firstprepared through an arc melting process. The alloy 1 was inserted into asilica tube 3 having a front end formed with a small opening 2, andmolted using a high-frequency coil 4. Then, the silica tube 3 wasdisposed immediately above a copper mold 6 formed with a vertical hole 5having a diameter of 0.5 to 2 mm to serve as a casting space, and agiven pressure (1.0 Kg/cm²) of argon gas was applied onto the moltenmetal 1 in the silica tube 3 to inject the molten metal 1 from the smallopening 2 (diameter: 0.5) of the silica tune 3 into the hole 5 of thecopper mold 6. The injected molten metal was left uncontrolled andsolidified to obtain a cast bar having a diameter of 0.5 mm and a lengthof 50 mm.

Table 1 shows the respective alloy compositions of Inventive Examples 1to 14 and Comparative Examples 1 to 7, and the respective Curietemperatures (Tc), glass transition temperatures (T_(g)) andcrystallization temperatures (T_(χ)) of Inventive Examples 1 to 14measured using a differential scanning calorimeter. Further, thegenerated heat value due to crystallization in a sample was measuredusing a differential scanning calorimeter, and compared with that of acompletely vitrified strip prepared through a single-roll rapid liquidcooling process to evaluate the volume fraction of a glass phase(Vf-amo.) contained in the sample.

Table 1 also shows the respective saturation magnetizations (Is) andcoercive forces (Hc) of Inventive Examples 1 to 14 measured using avibrating-sample magnetometer and an I—H loop tracer.

TABLE 1 Diameter T_(g) T_(χ) T_(χ) − T_(g) Is Hc Alloy Composition (mm)(K) (k) (K) T_(g)/T_(m) V_(f-amo.) (T) (A/m) Inventive Example 1(Fe_(0.75)B_(0.15)Si_(0.10))₉₉Nb₁ 0.5 815 858 43 0.56 100 1.50 3.7Inventive Example 2 (Fe_(0.75)B_(0.15)Si_(0.10))₉₈Nb₂ 1.0 812 870 580.57 100 1.49 3.5 Inventive Example 3 (Fe_(0.75)B_(0.15)Si_(0.10))₉₆Nb₄1.5 835 885 50 0.61 100 1.48 3.0 Inventive Example 4(Fe_(0.75)B_(0.15)Si_(0.10))₉₄Nb₆ 1.0 820 865 45 0.58 100 1.46 3.0Inventive Example 5 (Fe_(0.75)B_(0.15)Si_(0.10))₉₂Nb₈ 0.5 815 855 400.57 100 1.43 3.5 Inventive Example 6(Fe_(0.775)B_(0.125)Si_(0.10))₉₈Nb₂ 0.5 760 805 45 0.56 100 1.51 3.0Inventive Example 7 (Fe_(0.775)B_(0.125)Si_(0.10))₉₆Nb₄ 1.0 755 810 550.59 100 1.49 2.5 Inventive Example 8 (Fe_(0.75)B_(0.15)Si_(0.10))₉₉Zr₁0.5 815 870 55 0.58 100 1.53 2.8 Inventive Example 9(Fe_(0.75)B_(0.15)Si_(0.10))₉₈Zr₂ 0.5 810 860 50 0.58 100 1.51 3.0Inventive Example 10 (Fe_(0.75)B_(0.15)Si_(0.10))₉₆Hf₄ 0.5 820 865 450.59 100 1.47 3.0 Inventive Example 11 (Fe_(0.75)B_(0.15)Si_(0.10))₉₄Hf₆1.0 815 865 50 0.60 100 1.45 3.0 Inventive Example 12(Fe_(0.75)B_(0.15)Si_(0.10))₉₆Ta₄ 0.5 845 890 45 0.59 100 1.46 3.0Inventive Example 13 (Fe_(0.75)B_(0.15)Si_(0.10))₉₄Ta₆ 1.0 830 880 500.60 100 1.45 2.7 Inventive Example 14(Fe_(0.74)Ga_(0.33)B_(0.14)Si_(0.09))₉₈Nb₂ 0.5 780 820 40 0.59 100 1.483.0 Comparative Example 1 Fe₇₅B₁₅Si₁₀ 0.5 crystalline ComparativeExample 2 (Fe_(0.75)B_(0.15)Si_(0.10))_(99.5)Nb_(0.5) 0.5 crystallineComparative Example 3 (Fe_(0.775)B_(0.125)Si_(0.10))_(99.5)Nb_(0.5) 0.5crystalline Comparative Example 4(Co_(0.705)Fe_(0.045)B_(0.15)Si_(0.10))_(99.5)Nb_(0.5) 0.5 crystallineComparative Example 5 (Fe_(0.75)B_(0.15)Si_(0.10))₈₉Nb₁₁ 0.5 crystallineComparative Example 6 (Fe_(0.8)B_(0.2))₉₆Nb₄ 0.5 crystalline ComparativeExample 7 (Fe_(0.8)Si_(0.2))₉₆Nb₄ 0.5 crystalline

Further, the vitrification in each of the cast bars of InventiveExamples 1 to 14 and Comparative Examples 1 to 7 was checked throughX-ray diffraction analysis, and the sample sections were observed by anoptical microscope.

In Inventive Examples 1 to 14, the supercooled-liquid temperatureinterval (ΔT_(χ)) expressed by the following formula: ΔT_(χ)=T_(χ)−T_(g)(wherein T_(χ) is a crystallization temperature, and T_(g) is a glasstransition temperature) was 40 K or more, and the volume fraction(V_(f-amo.)) of a glass phase was 100% in the form of a cast bar with adiameter of 0.5 to 2.0 mm.

In contrast, Comparative Examples 1 which contains the element M in anamount of 1 atomic % or less or contains no element M were crystallinein the form of a cast bar with a diameter of 0.5 mm. While ComparativeExample contains Nb as the element M, the content of Nb is 11 atomic %which is outside the alloy composition range of the present invention.As a result, it was crystalline in the form of a cast bar with adiameter of 0.5 mm. Comparative Examples 6 and 7 containing 4 atomic %of the element M but no Si or B were crystalline in the form of a castbar with a diameter of 0.5 mm.

FIG. 1 is an optical micrograph showing the sectional structure of theobtained cast bar with a diameter of 1.5 mm. In the optical micrographof FIG. 1, no contrast of crystal particles is observed. This clearlyproves the formation of metallic glass.

All of Inventive Examples has a high saturation magnetization of 1.4T ormore. In particular, Inventive Examples 1 to 3 and 6 to 8 have a highsaturation magnetization of 1.5T despite of high glass forming ability.

INVENTIVE EXAMPLE 15

A molten alloy with the same composition as that of Inventive Example 1was rapidly solidified through a conventional melt-spinning process toprepare a ribbon material having a thickness of 0.025 mm and a width of2 mm. FIG. 2 shows thermal analysis curves of the cast bar obtained inInventive Example 1 and the ribbon material obtained in InventiveExample 15. As seen in FIG. 2, there is not any difference between theribbon material and the bulk material.

INVENTIVE EXAMPLE 16

A molten alloy with the same composition as that of Inventive Example 3was rapidly solidified through a conventional melt-spinning process toprepare a ribbon material having a thickness of 0.025 mm and a width of2 mm. FIG. 3 shows thermal analysis curves of the cast bar obtained inInventive Example 3 and the ribbon material obtained in InventiveExample 16. As with the above case, no difference is observed betweenthe ribbon material and the bulk material in FIG. 3.

FIG. 4 shows I—H hysteresis curves of the cast bar obtained in InventiveExample 1 and the ribbon obtained in Inventive Example 15, based on themeasurement of their magnetic characteristics using a vibrating-samplemagnetometer. These curves show that both the Inventive Example 1 and 15exhibit excellent soft magnetic characteristics.

FIG. 5 shows I—H hysteresis curves of the cast bar obtained in InventiveExample 3 and the ribbon obtained in Inventive Example 16, based on themeasurement of their magnetic characteristics using a vibrating-samplemagnetometer. These curves show that both the Inventive Example 3 and 16exhibit excellent soft magnetic characteristics.

INDUSTRIAL APPLICABILITY

As mentioned above, the Fe—B—Si-base metallic glass alloy of the presentinvention has excellent glass forming ability which achieves a criticalthickness or diameter of 1.5 mm or more and allows metallic glass to beobtained through a copper-mold casting process. Thus, the presentinvention can practically provide a large metallic glass product havinghigh saturation magnetization.

1. A soft magnetic Fe—B—Si-based metallic glass alloy product comprisingmetallic glass alloy being represented by the following compositionformula:(Fe_(1-a-b)B_(a)Si_(b))_(100-χ)M_(χ,) wherein a and b represent anatomic ratio, and satisfy the following relations: 0.125≦a≦0.17,0.10≦b≦0.15 and 0.225≦a+b≦0.3 M is one or more elements selected fromthe group consisting of Zr, Nb, Ta, Hf, Mo, Ti, V, Cr. Pd and W, and χsatisfies the following relation: 1 atomic %≦χ≦10 atomic %. wherein saidmetallic glass alloy has a supercooled-liquid temperature interval(ΔT_(χ)) of 40 K or more, a reduced glass-transition temperature(T_(g)/T_(m)) of 0.56 or more, said glass alloy product as cast hasminimum thickness or diameter of 0.5 mm or more, and a volume fraction(Vf-amo) of a glass phase is 100%, and a saturation magnetization ofmore than 1.4 T and coercive force of 3.7A/m or less.
 2. The softmagnetic Fe—B—Si-based metallic glass alloy as defined in claim 1, whichcontains 3 atomic % or less of one or more elements selected from thegroup consisting of P, C, Ga and Ge.